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Winter bivy sacks had been first developed as solo shelters for mountaineering and climbing the place contributors had been thinking about light-weight and extremely compressible tenting gear. Bivy Sacks are additionally a gorgeous choice for backpacking hunters, backcountry skiers, and winter backpackers who need the lightest and smallest shelter they will carry for in a single day or emergency use.

Winter bivy sacks are totally different from three-season bivy sacks which are sometimes used at the side of a tarp for insect and splashback safety, the place rain hitting the bottom can bounce again and moist your quilt or sleeping bag.  In distinction, a winter bivy sack is meant as a standalone shelter all by itself or at the side of a snow shelter reminiscent of a trench or snow cave. Winter bivy sacks are typically a lot greater in quantity to carry winter-weight sleeping luggage with out compressing the insulation and work greatest in dry and chilly circumstances the place precipitation is within the type of snow.

Winter Bivy Sacks – Benefits

The largest benefit of a winter bivy sack is the power to make use of it wherever you need to cease and sleep. Most fashions don’t require tent stakes or tent poles and so they pack up very small which is a bonus if you need to maintain your winter gear light-weight and compact. Most winter bivy sacks are made with waterproof/breathable prime materials to assist scale back inner condensation and waterproof base materials to maintain your sleeping bag and pad dry. Insect netting can also be accessible in some chilly climate bivy sacks and will be helpful after they’re utilized in spring circumstances when bugs start to emerge,

There are lots of benefits to sleeping in a water-resistant bivy sack over a tent. It’s simple to discover a place to place a bivy sack at night time because it solely requires as a lot house as your sleeping pad and sleeping bag. Merely unroll your bivy sack, slip your sleeping pad and sleeping bag inside, and crawl in. This makes them appropriate for sleeping on slim mountain ledges or in forested glades the place there’s simply sufficient house to lie between two timber.

Bivy sacks will be arrange nearly wherever with out the necessity for tent guylines or stakes

There are not any tent stakes to freeze into the bottom so you will get inside directly and get heat. Being waterproof, you don’t should lie on prime of a groundsheet both, because the backside of a water-resistant bivy sack is designed to maintain you dry. Bivy sacks additionally add a number of levels of insulation to your sleep system and make nice emergency shelters for solo winter hikers, offered you carry a sleeping pad and sufficient insulation to get by way of the night time.

Winter Bivy Sacks – Disadvantages

Bivy sacks are far more confining than tents, with solely sufficient house for you and some small private gadgets. You’ll be able to’t actually do something inside one besides take heed to podcasts or fall asleep. It’s awkward to alter out of your moist garments or placed on dry garments inside relying on the kind of bivy sack you’ve got, it may be rattling arduous to place in your boots, even to go for a pee at night time. There’s no place to retailer your backpack and the remainder of your gear will probably be totally uncovered an evening with none cowl.

Bivy sacks are additionally extra liable to inner condensation than a tent, even when manufactured with waterproof breathable supplies. You’re greatest off holding them open or unzipped at night time to scale back the temperature differential between the within of the bivy and the surface which causes condensation to type. Tent condensation happens for a similar motive however tents have higher air flow and extra quantity, so it’s simpler to maintain your sleeping bag dry when it happens.

Regardless of these disadvantages, I’ve buddies who swear by their winter bivy sacks as a result of they’re so quick to deploy in comparison with a tent or tarp. I’ve used winter bivy sacks and might recognize their strengths, however winter nights final a really very long time and it’s good to have a bit further house to alter your garments or sleep along with your gear inside your tent. Whichever you select although, actually is determined by what you’re attempting to perform.

The Outside Analysis Helium Bivy has a hooped design that you simply enter and exit from the entrance.

Comparability Desk

Forms of Winter Bivy Sacks

There are three kinds of winter bivy sacks to select from:

Hooped bivy sacks
Sleeping bag covers

The hooped design has a gap on the entrance, often supported by a curved fiberglass hoop. You might have crawl into it feet-first, and head-first, in your arms and knees, to get out. The entrance entrance is often screened with a stable cowl that may be zippered closed for heat or to dam wind or rain. This design offers good air flow on your head and helps to expel the water vapor contained in your breath. Whereas the additional room above your head additionally makes a hooped bivy really feel much less claustrophobic, in addition they are typically the heaviest sort of bivy bag accessible. The Outside Analysis Helium Bivy is an effective instance of the hooped design

The Black Diamond Bipod Bivy has a hooped design that gives head safety and is entered from the aspect.

One other variant of the hooped design offers a coated rear-facing compartment for the top utilizing a hooped pole.  This makes it simpler to get out and in at night time and to place in your footwear. You may also open up the highest of the bivy sack for higher air flow to mitigate inner condensation. The Black Diamond Bipod Bivy and the Huge Agnes Three-Wire Bivy are good examples of these bivy sort.

The MSR Professional Bivy is formed like a sleeping bag with a easy slit to get out and in of.

The best and lightest weight winter bivy sacks are little greater than sleeping bag covers. Some have drawstrings that you would be able to pull closed over your head, some have formed mummy-style hoods or easy slits above the face for air flow. Whereas not as livable or well-ventilated because the clamshell or snorkel-style bivy sack designs described above, they do get the job achieved if you’d like a extremely compressible, ultralight climate safety on your sleep system. The MSR Professional Bivy and the Black Diamond Twilight Bivy are consultant examples of the sleeping bag cowl design.

How you can Select a Winter Bivy Sack

There are a number of options and trade-offs to contemplate when selecting a winter bivy sack.

Waterproof/breathable prime cloth

Having a water-resistant/breathable prime cloth is vital to vent water vapor and assist reduce inner condensation that may make your sleeping bag moist. Nonetheless, not like rain jackets, most bivy sack producers don’t checklist the laboratory measurements used to charge waterproofing (hydrostatic head, abbreviated “HH”) or breathability (movable water transmission charge, abbreviated “MVTR”). That may make efficiency comparisons between totally different bivy sacks tough.

Extra headroom

If headroom is vital to you, take into account getting a bivy shelter with a hooped design. These bivy sacks include a versatile fiberglass pole that slides into the hood space to create extra quantity round your face and shoulders. The tradeoff is that they are typically heavier than extra minimal bivy sacks.

Extra quantity

Winter bivy sacks are typically excessive quantity to suit chilly climate winter sleeping luggage and inflatable pads with a excessive R-value. When selecting a bivy sack you need to be sure that there’s sufficient room on your sleeping bag to totally loft and that it’s not compressed by having a decent match.

Entrance and exit

It’s a lot simpler to get out and in of a bivy sack that has a zipper alongside the aspect than one which solely has a “hatch” on the head finish, to crawl out and in off. You’ll keep drier if the bottom is roofed in snow and it’s a lot simpler to placed on and take off your footwear.

Insect netting for hotter temperatures

Should you plan to bivy in early spring when biting bugs emerge, be sure that to get a winter bivy sack with a mesh panel over the face so you’ll be able to sleep with out bugs biting your face at night time. Should you solely plan to sleep in a bivy sack in winter or in snow caves, a mesh panel will probably be much less vital. For hotter climate use, I’d encourage you to spend money on an ultralight bivy sack or bug shelter reasonably than a winter bivy sack, since they’re a lot cooler to make use of. See our 10 Finest Backpacking Bug Shelters for our really helpful three-season bivy sacks.

Weight and Packed Dimension

Don’t neglect to contemplate the burden of the bivy sack and its packed dimension, since one of many chief advantages of utilizing a bivy sack is gear weight and dimension discount. There’s usually a tradeoff between options and weight/dimension, however some winter bivy sacks are surprisingly light-weight and compressible.

Sizing and Match

When doubtful, order a bivy sack (examine the retailer’s return coverage) and lie in it at residence to see if it matches. This may most likely inform you much more about whether or not it is going to give you the results you want than evaluating the specs of a number of fashions listed on-line. Verify to just be sure you can suit your sleeping pad and sleeping bag inside, and that the foot field is massive sufficient on your ft.

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